Jaw lock for automatic screwdriver



United States Patent Inventor Kenneth R. Bangerter Ithaca, N.Y.

Appl. No. 779,968

Filed Nov. 29, 1968 Patented Dec. 15, 1970 Assignee lngersoll-Rand Company New York, N.Y. a corporation of New Jersey JAW LOCK FOR AUTOMATIC SCREWDRIVER 5 Claims, 6 Drawing Figs.

US. Cl 144/32, 206/56 Int. Cl B27b 17/00 Field of Search 144/32; 206/56(DF) [56] References Cited UNITED STATES-PATENTS 1,082,771 12/1913 Russell Primary Examiner-Gerald A. Dost Attorneys-Carl R, Horten and David W. Tibbott ABSTRACT: An automatic screwdriver having a head carrying a pair of pivoted jaws and adapted to periodically feed screws into the head between the pivoted jaws as they are needed. A U-shaped fork is pivoted on the side of the head to swing over the forward ends of the jaws for locking the jaws to prevent them from opening during the delivery of a screw. A mechanical leg is pivoted on the fork and extends forward of the head for engaging a work surface to swing the fork out of its locking position during the final stages of driving the screw. The fork is resiliently biased toward its locking position.

PATENTED DEC] 5 I970 INVENTOR KENNETH R. BA/VGEHTER ATTORNEY .IAW LOCK FOR AUTOMATIC SCREWDRIVER BACKGROUND OF INVENTION This invention relates to power tools for applying fasteners and more particularly to automatic screw screwdrivers of the type that automatically feed fasteners to the screwdriver head as they are used.

In general, automatic screwdrivers use a head having a Y- type connecting joint interconnecting a screw feeding conduit to the head between the screw holding jaws and the driving blade. The screw holding jaws are pivoted on opposite sides of the head to grasp a screw between them. Normally, the driving blade earns the jaws open as it passes between them to release the screw as it is driven home by the driving blade. The screw is blown into place between the jaws by compressed air and, because the jaws are resiliently held together merely by springs, there is the danger that the jaws will be cammed open by the rapidly moving screw which will then be shot" from the screwdriver. This danger becomes greater as the jaw springs weaken during the normal wear life.

SUMMARY OF THE INVENTION The principal object of this invention is to eliminatethe foregoing danger of screws being shot from the screwdriver and to provide a means for locking the jaws against opening prematurely.

Other important objects are: to provide a locking means for the jaws of a fastener applying tool which automatically releases the jaws as they approach a work surface; and to provide a novel means for automatically unlocking the fastener holding jaws of a power tool in response to the approach of the jaws to a work surface.

The foregoing objects are generally attained in a power tool having a head carrying a pair of pivoted jaws for grasping a fastener therebetween and a pivoted locking fork adapted to swing to a locking position over the jaws to prevent them from opening. Means is provided to resiliently urge the fork to its locking position. The invention further includes release means operative to pivot the fork away from its locking position as the head of the tool approaches a work surface during the final stages of driving a fastener. In general, the release means is a mechanical link projecting forward from the head of the tool and adapted to engage the work surface to apply a torque force on the fork acting to swing it away from its locking position.

BRIEF DESCRIPTION OF DRAWING The invention is explained in connection with the accompanying drawing wherein:

FIG. 1 is an elevational view of an automatic screwdriver using the jaw lock means of this invention;

FIG. 2 is an enlarged fragmentary elevational view of the front end of FIG. 1 taken at right angles and with the fastener jaws closed;

FIG. 3 is a section taken on line 3-3 of FIG. 2;

FIG. 4 is a longitudinal section taken on line 4-4 in FIG. 3;

FIG. 5 is a fragmentary elevation similar to FIG. 2 with the jaws open; and

FIG. 6 is a section taken on line 6-6 in FIG. 4.

DESCRIPTION OF PREFERRED EMBODIMENT The automatic screwdriver 1 shown in FIG. 1 conventionally includes a body 2 having a front end or head 3. Conventional hoses are connected to the read end of the body 2 and are not described because they form no part of this invention. The head 3 includes an annular nose washer 4 located on its front surface and a pair of jaws 5 pivoted on pivots 6 in slots fonned in the head 3 behind the nose washer 4. The nose washer 4 is adapted to abut a work surface at the end of driving a screw. The jaws 5 are resiliently urged toward each other to grasp a screw between them. The head 3 also includes a screw feeding conduit 7 entering the side of the head at an angle extending generally forward and adapted to deliver a screw into the head between the jaws 5. All of the foregoing structure is conventional and is shown in the expired US. Pat. No. 2,534,l40 issued to E. S. Moore on Dec. 12, I950.

The invention in this application is the provision of a means for locking the jaws 5 together during the delivery of a screw between the jaws 5. This means is adapted to release the jaws 5 in order for them to open during the final driving cycle of the screwdriver. This jaw holding means includes a fork 8 pivoted on the side of the head 3 on a pivot axis 9 and having a pair of spaced arms 10 forming a U-shaped cross section adapted to pivot forward and extend partially over the forward ends of the jaws 5, thereby preventing them from pivoting open.

A spring 11 is mounted on the head 3 with a portion extending resiliently over the fork 8 to urge it forwardly and inwardly to its locking position over the jaws 5. Locking the jaws 5 closed prevents them from accidentally opening during the delivery of a screw through the conduit 7. Inadvertent opening of the jaws 5 during the delivery of the screw would allow the screw to be shot from the screwdriver in the manner of a projectile, which, of course, is very undesirable and dangerous.

The fork 8 includes a short leg 14 pivoted in a kerf formed in the central portion of the fork on a pivot axis 15 and projecting a short distance forward of the nose washer 4. The leg 14 is provided with appropriate stops so that it is always inclined inwardly and forwardly relative to a line extending through the two pivot axes 15 and 9; hence, the leg 14 is always positioned away from an alignment dead center with these two pivot axes. Preferably, the forward end of the leg 14 is angled so that its inner edge 16 is located forwardly of the remainder of the remainder of the front surface of the leg 14.

Looking at FIG. 2, as a screw 17 is driven by the screwdriver 2, the nose washer 4 and the leg 14 approach the work surface 18. Eventually, the inner edge 16 of the leg 14 engages the work surface 18 and further forward movement of the screwdriver causes the leg 18 to apply a force on the fork 8 acting rearwardly and outwardly causing the fork to pivot outwardly to release the jaws 5 as shown in FIG. 5. Thereafter, the jaws 5 are free to open as the screw 17 is driven home as is conventional in automatic screwdrivers.

After the driving of the screw 17 is completed and the operator lifts the screwdriver from the work surface, the fork 8 is automatically returned to the locking position shown in FIG. 2 preventing the jaws 5 from opening during the delivery of another screw through the conduit 7 into the head 3.

Although only a single embodiment of the invention has been illustrated and described in detail, it is understood that the invention is not limited thereto. Various changes can be made in the disclosed arrangement without departing from the spirit and scope of the invention as set forth in the accompanying claims.

I claim:

1. A power tool including:

a head carrying a pair of pivoted jaws for grasping a fastener therebetween;

lock means movable to a locking position locking said jaws together;

means urging said lock means to its locking position; and

release means operative to move said lock means from its locking position in response to the approach of said jaws to a work surface to release the fastener grasped within said work jaws.

2. The power tool of claim 1 wherein: said lock means includes a U-shaped fork having a pair of spaced arms adapted to fit over said jaws to hold them closed.

3. The power tool of claim 2 wherein: said fork is pivoted on said head and is urged to its locking position by a spring.

4. The power tool of claim 3 wherein: said release means engages the work surface and applies a force on said fork moving it from its locking position.

5. The power tool of claim 4 wherein: said release means is a link pivoted on said fork remote from the pivot of the fork on the head and positioned to apply a torque force on said forl in re s ponse toenga gement with the work surface, to swing the fork from its locking position. 

